What Can Nanoparticles Tell Us About Knapweed Invasions?

December 9th, 2011

By: Ylva LekbergPh.D. Ecologist

Spotted Knapweed (Centaurea stoebe) is a noxious weed from Eurasia that has invaded MPG Ranch. These invasions may be aided by soil-dwelling arbuscular mycorrhizal fungi (AMF) because knapweed becomes more successful than native plants in the presence of AMF. It is suspected that knapweed is exploiting fungal symbiosis somehow, but the mechanism is unknown. In collaboration with Dr. Matthew Whiteside from University of British Columbia, we designed an experiment to calculate the cost-benefit relationship of mycorrhiza when knapweed is competing with native grasses. We will measure carbon allocation from plants to fungi by stable isotope probing, and reciprocal phosphorus delivery from fungus to plant using fluorescent nanoparticles. Combining these methods will help us to determine if knapweed truly pays its dues to the fungus, or is a successful cheater.

Picture 1: Half the plants in each pot are labeled with non-radioactive ¹³CO₂ gas that the plants incorporate through photosynthesis. We can then trace this carbon source throughout the plant and measure how much is allocated to the soil in general and to AMF in particular.

Picture 2: Quantum dots fluoresce under UV-light and can be bound to any molecule. We use phosphorus-labeled quantum dots that we add to pots to trace P movements from AMF to plants.

About the Author

Ylva Lekberg

Ylva graduated from the Swedish University of Agricultural Sciences with a M.Sc. in Biology and Horticulture in 1996 and a Ph.D. in Ecology from Penn State University in 2004. She received the Alumni Association Dissertation Award for her work in agroecology and subsistence farming in Sub-Saharan Africa. Post-doctoral positions at Montana State University and later at Copenhagen University as a Marie Curie Fellow allowed her to explore the role of arbuscular mycorrhiza, a root-fungus symbiosis, for geothermal plants in Yellowstone National Park and coastal grasslands in Denmark. Her research has been published in international journals such as Nature Communications, Ecology Letters, and New Phytologist.

Ylva joined MPG Ranch in 2010. Since then, she has explored how invasive plants common to western Montana, including spotted knapweed (Centaurea stoebe), leafy spurge (Euphorbia esula) and cheatgrass (Bromus tectorum), influence soil microbial community composition and function, and how this in turn may affect invasive success. A lot of her research also focuses on the AM symbiosis in terms of community ecology and physiology. A current project addresses how exchange ratios in this symbiosis may differ among co-occurring plants and depend on soil nutrient availabilities. She uses surveys, field and greenhouse experiments, and literature approaches such as meta-analyses to address questions. To learn more about research and publications from Ylva and her group, see CV below and the Soils, Plants and Invasion section.

In addition to her work at MPG Ranch, Ylva is an adjunct professor at University of Montana at the Department of Ecosystem and Conservation Sciences.